3To assemble tostadas, spread 1/2 cup beef mixture onto each tostada shell. Place carrots in center of each for nose, red bell pepper slice for mouth and 2 cherry tomatoes for eyes. Spoon 1/4 teaspoon sour cream on each tomato eye; top with olive slices. Sprinkle 1/4 cup cheese and 1/4 cup lettuce around top edge of each tostada. Place tortilla chip on top of each tostada for scarecrow hat. Serve immediately.